RENAL FUNCTION IN CYSTIC FIBROSIS

Abstract

The main diagnostic criteria in cystic fibrosis (CF) is an elevated concentration of sodium chloride in sweat. As the kidney is the main regulator of sodium homeostasis it was of special interest to study renal function in CF. Sixteen patients with CF, 5-19 years of age, were studied. Oral and intravenous (iv) sodium load tests were performed including clearances of inulin and PAH. Standardized clearance technique was used. Glomerular filtration rate (GFR) and filtration fraction (FF) were increased compared to controls. Renal plasma flow was normal. Basal urinary sodium excretion as well as renal responses to oral and iv sodium loads were low indicating an increased renal sodium reabsorption. Diluting capacity was decreased because of a low distal sodium delivery indicating an increased proximal sodium reabsorption. Ten CF-children were treated with IntralipidR at regular intervals for one year. The GFR decreased to normal values and the urinary elimination rate of an oral sodium load was still low but increased significantly compared to that before treatment. The increased GFR and proximal sodium reabsorption found in CF might be due to a change in fatty acid composition of the cell membrane and/or a disturbance of the prostaglandin metabolism.